ISSN:0884-0431    

DOI:10.1002/jbmr.5650020302

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractDevitalized, neonatal, rat calvariae incubated in a buffered solution release Ca2+and P1during the first day into the medium until levels reach 1.2 mMand 2.6 mM, respectively. Thereafter levels gradually decrease to stabilize by the fifth day at 0.5 mMand 2 mM. Comparison of these solubility changes with those of known calcium phosphate salts suggests that calvarial solubility is controlled by a mixture of impure, soluble, apatite precursors, which at cell death transform to an impure apatite. Increasing concentrations of Mg2+increased the rate of Ca2+release and, at 3 mM, stabilized Ca2+by the fifth day at 0.9 mM. Decreasing the pH from 7.4 to 7.2 produced similar solubility changes as did the addition of citrate at 0.3 mM, phosphocitrate at 0.3 mM, ATP at 0.1 mM, and the bisphosphonate, HEBP, at 0.1 mM. Osteocalcin did not increase calvarial solubility but was able to slow the rate of calcium phosphate phase transition if present at the time ofin vitrocrystal formation. Phosphocitrate and HEBP were also more effective when present duringin vitrocrystal formation. HEBP was most effective when present during biological crystal formation, as shown by the increased solubility of devitalized calvariae removed afterin vivoadministration of HEBP.In vivomanipulations of osteoclast activity produced changes in plasma calcium which correlated with the solubility of the corresponding calvariae after removal and devitalization. Low milk intake increased calvarial solubility. Increasing doses of 1,25(OH)2D3increased plasma calcium and calvarial solubility, both of which were reversed by injection of acetazolamide.It was concluded from this survey of devitalized bone solubility that calcium exchange between bone and body fluids can buffer calcium homeostasis in the young rat. The exchange is passive. The active components appear to be osteoblastic formation of soluble apatite precursors and their stabilizers and, in reverse, osteoclastic transformation of apatite to precursors by H2CO3secretion.

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020303

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractWe compared three antirheumatic agents: auranofin (Aur), gold sodium thiomalate (GST), and penicillamine (Pen) for their effect on resorption in control unstimulated cultures of fetal rat long bones and in cultures stimulated by parathyroid hormone (PTH), prostaglandin E2(PGE2), and murine interleukin‐1 (mIL‐1). Aur (3 × 10−6M) and GST (10−4M) inhibited PTH‐stimulated bone resorption by 39 and 42%, respectively. The same concentrations of Aur and GST inhibited PGE2‐stimulated bones by 72 and 44, respectively, and mIL‐1‐stimulated bones by 74 and 50%, respectively. Pen (10−4M) was not effective against any of the stimulators. Dose‐response curves showed that Aur was at least 10 times more potent than GST. Inhibition by Aur was sustained after removal of the drug, while there was full recovery from GST. Aur inhibited3H‐thymidine and3H‐proline incorporation into bones, while GST had no effect. Aur and GST decreased β‐glucuronidase activity to undetectable levels at five days of culture. Part of the therapeutic effectiveness of Aur and GST may reside in their ability to inhibit periarticular destruction by inhibiting PGE2‐ and IL‐1‐medi

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020304

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractA tissue‐specific protein fraction has been detected in rat osteogenic tissue. Dissociative extraction of adult rat bone matrix with 4Mguanidinium chloride solution was followed sequentially by gel chromatography and Polyacrylamide gel electrophoresis. By the latter procedure a prominent protein component of molecular weight 19,000 was isolated from the low molecular weight fraction, and antibodies directed against this protein were raised in rabbits. The antibodies were mainly against antigenic sites on this protein, as shown by protein blotting techniques. By embedding rat tissues in hydrophilic plastic and by using immunohistochemical procedures the presence of this protein was demonstrated specifically in bone matrixin vivo, in osteogenic tissue developing in diffusion chamber culture, and in a malignant osteoblast cell line (UMR 106). Soft tissues (liver, kidney, spleen, gut, skin, thymus, eye) showed no reactivity with the antiserum andin vitro afurther malignant osteoblast cell line (ROS 17/2.8) did not synthesize the 19,000 molecular weight protein. This protein appears to be expressed solely by osteogenic tissue and may be used as a biochemical criterion of osteogenic differentiatio

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020305

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractSince bone mass has been shown to be an important determining factor of fracturesin vitro, we undertook a study to evaluate whether bone mass measurements could separate postmenopausal women with vertebral compression fractures from women of a similar age without fractures. We also wanted to see if methods of measuring bone mass at the spine would be more sensitive or specific than methods that measured bone at the wrist or the entire skeleton. The techniques used were: total body calcium by neutron activation analysis (TBC), single photon absorptiometry (SPA), dual photon absorptiometry (DPA), and quantitative computed tomography (QCT). Normal women aged 20–85 were measured, but only those>50 yr were used in the analysis. Mean values for women with fractures were significantly lower than normals (p<.001): TBC 642 ± 103 g vs. 764 ± 114; SPA .658 ± .134 g/cm vs. .779 ± .142; DPA 3.75 ± .82 g/cm vs. 4.37 ± .86; QCT 59.0 ± 25.7 mg/cc vs. 92.6 ± 36.0. However, each of the methods showed considerable overlap between women with and without fractures. At 90% specificity the sensitivities of the tests were: TBC 34%; SPA 29%; DPA 33%; QCT 36%. When values were expressed as the % expected (based on age and height) then the sensitivities were: TBC 52%; SPA 36%; DPA 35%; QCT 44%. Using Bayes' theorem, we constructed curves showing the posttest probability of these tests at a prevalence of 20%. None of these bone mass measuring techniques showed complete separation between normal and osteoporotic women with fractures; about one‐half of the women with fractures were below the normal range. The risk of having a fracture increases as bone mass declines, but our data suggest that bone mass is not the only factor leading to vertebral fractures in postmenop

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020306

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractWe previously demonstrated in normal subjects that 1,25‐dihydroxyvitamin D3(1,25(OH)2D) can prevent the increase in serum 25‐hydroxyvitamin D (25‐OHD) which occurs in response to vitamin D. An investigation was carried out in eight normal subjects, therefore, to determine whether increases in calcium intake would alter the response of serum 25‐OHD to challenge with vitamin D. In control studies, vitamin D, 100,000 U/d for 4 d, significantly increased mean serum 25‐OHD from 18 ± 3 to 42 ± 5 ng/ml (p<0.001), an increment of 24 ng/ml (133%). Mean serum calcium, ionized calcium, phosphorus, creatinine, and 1,25(OH)2D did not change. In contrast, the same dose of vitamin D and calcium, 2,000 mg/d for 4 d, administered to the same eight subjects produced an increase in mean serum 25‐OHD from 19 ± 3 to 31 ± 4 ng/ml (p<0.001), an increment of only 12 ng/ml (63%) and significantly less than the control (p<0.02). Mean serum calcium (8.8 ± 0.1 vs. 9.2 ± 0.1 mg/dl,p<0.01) and ionized calcium (4.79 ± 0.07 vs. 4.85 ± 0.08 mg/dl,p<0.05) increased significantly in response to vitamin D and calcium, mean serum phosphorus and creatinine did not change, and mean serum 1,25(OH)2D decreased significantly (37 ± 2 vs. 31 ±4 pg/ml,p<0.02). In a postcontrol study in six of the normal subjects, vitamin D again significantly increased mean serum 25‐OHD from 17 ± 3 to 39 ± 9 ng/ml (p<0.02), an increment of 22 ng/ml (129%). Urinary calcium increased significantly on each of the four days of the administration of calcium as compared to the control study. The results provide evidence that changes in calcium intake can modulate the me

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020307

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractEffect of citrate on the spontaneous precipitation of calcium oxalate was examined in synthetic media. Citrate significantly increased the formation product of calcium oxalate. This “direct” measure of inhibitor activity, representing activity product at the point of nucleation, rose by 76% by the addition of citrate sufficient to provide trivalent citrate concentration of 1.49 mM. Moreover, citrate inhibited calcium oxalate crystallization by complexing calcium and lowering calcium oxalate saturation. This “indirect” measure of inhibitor activity was assessed from the concentration product of calcium oxalate at the point of nucleation, since this measure should provide a reflection of both ion pair formation and direct inhibitor activity of citrate. The concentration product exceeded the formation product at all ionic (trivalent) citrate concentrations, particularly at high ionic citrate levels. At the ionic citrate concentration of 1.49 mM, the rise in the concentration product was 373%, which was nearly fivefold that observed for the formation product. The presence of ferric or aluminum cations at a physiologic concentration of 2 mg/l did not modify the increase in formation product produced by citrate. Thus, citrate inhibits calcium oxalate crystallization, largely by complexing citrate, but also by directly affecting nucleation. Presence of ferric or aluminum cations at a physiological concentration does not modify the inhibitor action of

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020308

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractThe proportion of trabecular bone in human cadaver vertebrae was assessed by anatomic dissection. Thirty‐two whole thoracic and lumbar vertebrae were obtained from 10 normal human postmenopausal female cadavers, 14 from 4 normal adult human male cadavers of similar age, and 8 from one female osteoporotic cadaver. Each vertebra was opened by saw cuts and separated into four tissue types: (1) body trabecular bone and marrow; (2) body cortical bone; (3) vertebral arch trabecular bone and marrow; and (4) vertebral arch cortical bone. Calcium was determined in each tissue type for each vertebra by ashing and atomic absorption spectrophotometry.Trabeculae accounted for 24.4 ± 4.5% of the total calcium in whole female vertebrae, and 18.8 ± 4.4% in whole male vertebrae (p<0.001). The body averaged 41.8% trabecular bone in females and 33.5% in males. The arch averaged 9.7% trabecular bone in females and 4.9% in males. The proportion of trabecular bone in the whole vertebrae in the single osteoporotic spine was 28.5 ± 3.2%, a value not significantly different from the trabecular fraction in normal females.These data indicate that whole human thoraco‐lumbar vertebrae are composed of a substantially lower proportion of trabecular bone than is usually assumed, and they suggest that cortical and trabecular bone are eventually lost in equal proportion from the vertebrae during the development of spinal osteoporosis. These results are important for the interpretation of data from noninvasive bone measurement techniques that evaluate the spine, and they suggest that studies of this type are important for any site where noninvasive bone mass measurement i

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020309

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractWe characterized the alkaline phosphatase activity of the human osteogenic sarcoma cell line, SAOS‐2, and studied the regulation of this enzyme and 3',5'‐cyclic adenosine monophosphate levels by 1,25‐dihydroxyvitamin D3and triamcinolone acetonide. We report that the basal alkaline phosphatase activity of SAOS‐2 cells was 100–1000 times greater than that of other established human osteogenic sarcoma cell lines. The enzymatic activity was thermolabile, could be inhibited by levamisole and L‐homoarginine, but not by L‐phenylalanine, and was immunoprecipitable with anti‐bone/liver/kidney, but not with anti‐placental antibody, confirming that it is the tissue‐unspecific or bone/liver/kidney isoenzyme. However, in contrast to other established human osteosarcoma cell lines (TE‐85, SAOS‐1), in which alkaline phosphatase activity is stimulated several‐fold by the steroid hormones 1,25‐dihydroxyvitamin D3and hydrocortisone, the alkaline phosphatase activity of SAOS‐2 cells was not affected by 1,25‐dihydroxyvitamin D3treatment despite the presence of classical receptors for this hormone. Furthermore, administration of the potent glucocorticoid analogue, triamcinolone acetonide, induced only a modest increase in activity. The SAOS‐2 cell line expressed low basal cAMP levels (28 pmol/106cells) which could be increased 25–40 times by pretreatment with parathyroid hormone. However, unlike other osteoblastic models, in which PTH‐induced cAMP stimulation is modulated by 1,25‐dihydroxy vitamin D3and glucocorticoids, neither of these hormones had an effect on the PTH‐stimulated cAMP levels in SAOS‐2 cells. We conclude that the SAOS‐2 cell line is an osteoblastic cell model which expresses high levels of tissue‐unspecific alkaline phosphatase activity and exhibits limited responsiveness to two steroid hormones. These cells may prove useful in determining the structure and processing of alkaline phosphatase and in studying other features of the osteoblastic phenotype, such as

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020310

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY

摘要:

AbstractIn vitroactivated human peripheral blood lymphocytes possess the receptor protein for 1α,25‐dihydroxyvitamin D3(1,25(OH)2D3). In the present study we have examined whether activated lymphocytes that occurin vivoin human thymuses and tonsils also possess receptors for 1,25(OH)2D3. Freshly isolated lymphocyte preparations, from five separate surgical specimens of thymus and tonsil, were depleted of monocytes and examined, before and after fractionation on a density gradient of Percoll, for [3H] 1,25(OH)2D3binding by means of sucrose density gradient sedimentation, by saturation analysis of the binding, and by DNA‐cellulose chromatography. The state of activation of the lymphocyte preparations was determined using [3H] thymidine incorporation, DNA and RNA quantitation (using acridine orange), and by determining the presence or absence of markers of activation (interleukin‐2 receptor, transferrin receptor, and HLA‐DR molecules). In both the thymic and the tonsillar lymphocyte preparations we detected a 1,25(OH)2D3‐binding molecule possessing sedimentation coefficient of 3.3 S and dissociation constant of 10−10Mas well as DNA binding capability. In thymic lymphocytes, the 1,25(OH)2D3receptor concentration correlated positively with the number of lymphocytes expressing the transferrin receptor (r= 0.84;p<0.05). In addition, in both thymic and tonsillar lymphocytes the concentration of 1,25(OH)2D3receptors correlated positively with the number of cells in the G1aphase of the cell cycle (r= 0.79,p<0.01, andr= 0.88,p<0.001 for thymic and tonsillar lymphocytes, respectively). In contrast, the 1,25(OH)2D3receptor concentration in these preparations did not correlate with the rate of cell proliferation. These results indicate that thymic and tonsillar lymphocytes in the early stages of activation possessin vivothe 1,25(OH)2D3receptor protein, and suggest that 1,25(OH)2D3may actin vivoon

ISSN:0884-0431    

DOI:10.1002/jbmr.5650020311

出版商:John Wiley and Sons and The American Society for Bone and Mineral Research (ASBMR)    

年代:1987

数据来源: WILEY